Investigators are trying to determine the cause of a three-alarm blaze that destroyed three houses in Birmingham's Southside overnight.

"We've got some things we're looking at, but right now we're not going to speculate," said Birmingham Fire and Rescue Battalion Chief C.W. Mardis. "We have a lot more to investigate."

Police officers on patrol spotted the blaze in the 2100 block of 10th Avenue South just after 1 a.m.

"It was pretty well involved and at that point is spread rapidly," Mardis said.

The fire began in the house at 2120 10th Ave. S., a building under renovation.

Because of work being done on the house, Mardis said, the walls were exposed and the fire traveled quickly to the roof. From the roof, it spread to the houses on either side, one of which was a law firm. Those addresses were 2124 and 2116.

It took firefighters two hours to contain the fires. They remained on the scene throughout this morning putting out hot spots.

All of the buildings were unoccupied, and are a total loss, Mardis said.